The Bible defines holy as something or someone that is separated (sanctified) and dedicated to serve and fulfill the will of God. This means that the Eternal considers them as sacred, blameless and pure for His use.
The English word "holy" is used 611 times in 544 verses in the King James (KJV) Bible. The related word "holiness" is recorded an additional 43 times. In the Old Testament alone "holy" is found 430 times in 375 verses. It is mentioned the most in the book of Leviticus (94) followed by Exodus (55).
The first Biblical verse to record this word is Exodus 3:5. Moses sees a flaming bush in the desert and goes to examine it. After discovering it was miraculously burning without being consumed he hears the voice of God speaking from the fire.
And he (God) said, Draw not nigh hither: put off thy shoes from off thy feet, for the place whereon thou standest is holy ground (Exodus 3:5, KJV).
Holy is found not only three times in two verses (Isaiah 6:3, Ezekiel 39:7) it is written four times in Ezekiel 42:13!
Holy, in the KJV New Testament, comes from the Greek hagios (Strong's #G40) and means pretty much the same as its Hebrew counterpart. The word itself is recorded 181 times in 169 KJV New Testament verses. The book of Acts contains the most occurrences with 52.
The only writings that do not contain this word are four books by the Apostle Paul (Galatians, Philippians, 2Thessalonians and Philemon) plus the general epistles of James, 2John and 3John. Interestingly, this same Greek word is also translated as "saints" in several places (Philemon 1:5, Hebrews 6:10, etc.).
Here is the patience of the saints (hagios): here are they that keep the commandments of God, and the faith of Jesus (Revelation 14:12, KJV).
The Bible is chock full of people, places, times, things and so on that are labeled holy.
Holy people included ancient Israel (Exodus 19:6, 22:31), and their children (Ezra 9:2), Aaron and his sons who were priests (Leviticus 21:1 - 6) and those taking the Nazarite vow (Numbers 6:8). Those directly called and chosen by God, like Elisha, were also set apart to serve him (2Kings 4:9).
Ground became sacred if the presence of God was on or near it (Exodus 3:5, Joshua 5:15). Jerusalem as a whole (Nehemiah 11:1) and all the cities given Israel (Isaiah 64:10) were considered set apart for the Eternal. This is why this area of the Middle East is considered the Holy Land (Zechariah 2:12).
God's annual Feast Days (Passover, Days of Unleavened Bread, Pentecost, etc., Leviticus 23), his weekly seventh-day Sabbath (Exodus 16:23) and the jubilee year (Leviticus 25:12) are considered sacred times.
The entirety of Israel's tabernacle in the wilderness, as well as Jerusalem's temple, including all their furnishings and the sacrifices offered, were holy to God (Exodus 26:34, 29:33, Leviticus 2:3, 1Chronicles 29:3). Even the oil Israel used for anointing, including the recipe used to make it, was considered sacred. Those who misused it or tried to duplicate it were punished by the Lord (Exodus 30:31 - 38).
The Holy Spirit is so called because it is the power through which God accomplishes his will (see our article on the trinity). This power is given to those who repent in order to aid their development in godly character (Psalm 51:11). The Bible is consider sacred because its words, in the original languages in which they were written, were inspired directly by God (2Timothy 3:15).